Balanced gear pump



W. ERNST Dec. 13, 1949 BALANCED GEAR PUMP Filed June 19, 1944 INVENTOR WALTER rmvsv;

BY A a I"; I 1 j ATTORNEY$ Patented Dec. 13, 1949 BAILAN ED GEAR PUMP Walter Ernst, Mount Gilead, Ohio, assignor to H-P-M Development Corporation,

Wilmington,

Del., a corporation of Delaware Application June 19, 1944, Serial No. 541,050 4 Claims. :(Cl. 103-126) This invention relates to hydraulic apparatus and, more particularly, to hydraulic pumps or motors.

This invention has for itsprincipal object the balancing of gear pumps or motors. In the usual type of gear pump or motor the gears or rotating pumping members are subjected to considerable thrust due to the operating pressures within the device. This unbalanced thrust causes severe bearing loads, excessive wear and ineflicient operation.

There is also present in gear pumps and motors another phenomenon which detracts from the performance thereof. As the gears rotate, in mesh, a certain amount of fluid is trapped in the space between consecutive teeth on one gear and beneath the tooth of the other gear disposed therebetween. The fluid s trapped is subjected to excessive pressure as the gears rotate and tends excessively to load the bearings and also to cause the device to be noisy in operation.

Accordingly, it is another object of this invention to provide a means for relieving the aforementionedentrapped fluid. I

It is another object of this invention to provide a full hydraulically balanced gear pump or motor in connection with the relief of the fluid entrapped at the point of contact of the said ears.

It is another object to provide a simplified and improved method for balancing a gear pump or motor such that the resulting product is more economical to produce and operates in an improved manner.

These and other objects will become more apparent upon reference to the following description taken in connection with the accompanying drawings, in which:

Figure 1 is a section through a gear pump or motor constructed according to this invention;

Figure 2 is a transverse section through the pump of Figure 1 and is indicated by the line 2-2 on Figure 1; and

Figure 3 is a view similar to Figure 1 but showing a somewhat modified construction.

Referring to the drawings and, particularly, Figures 1 and 2, there is illustrated a gear pump or motor having a casing ID with the ports II and I2. The casing I!) may comprise a member open on one side and closed by a plate l3 which is fastened thereto by the screws l4. Suitable sealing means such as the resilient ring I5 may be used to efiect a seal along the parting line of the members I3 and III.

Rotatably mounted within the casing III are the gears B and 1 which are in mesh at III. The gears are suitably journalled in the casing l0 and the plate l3 such as by the bearings l9 which are carried by the said casing and plate. The gears l6 and 11 are, preferably, integral with or firmly afiixed to the shafts with which they rotate.

The gears form, with the casing I0 and plate l3, the chambers 20 and 2|. If the device is to operate as a pump, the gears rotate in the direction of the arrows 22 in Figure 1 and continu- I ously draw fluid into the chamber 20 from the port while expelling fluid from the chamber 2| through the port l2.

Inasmuch as the chamber 2| is at discharge pressure while the chamber 20 is at suction pressure, the gears l6 and I1 are subjected to thrusts exerted thereon by the pressure fluid within the discharge chamber. For example, the thrust on the gear l6 extends toward the upper right from the chamber 2| while the thrust on the gear I! extends from the said chamber toward the lower right (Figure l).

In order to balance oflf the aforementioned thrusts there is provided a plurality of bores in the gears l6 and I1, these bores passing through the gears on diameters thereof and terminating at either end between pairs of teeth. The bores are indicated at 23 in Figures 1 and 2 and are arranged across the width of the gear so that each bore is separate from the others. It will be apparent that the gears l6 and I! must each comprise an even number of teeth in order that the bores 23 may effect hydraulic communication between the opposite tooth spaces. However, although the gears are shown to be of the same size, it will be apparent that they may be of any relative size without in any way influencing the operation of this invention.

Referring now to Figure 3, there is shown a pump or motor constructed similarly to the device of Figures 1 and 2 except that the casing I0 is provided with the spaces or notches 24 and 25 which are provided for the purpose of relieving "the fluid which is trapped at l8 as the gears rotate. The spaces 24 and 25 are located so that a tooth space approaching the zone I8 is in fluid communication therewith and continues in communication therewith until the entrapped fluid has been completely relieved.

Operation of the embodiment of Figures 1 and 2 Assume that the gears l6 and I! are being rotated as indicated by the arrows 22. Then, the chamber 2| is at discharge pressure and tends to tially equivalent conditions would prevail, the direction of rotation of the gears being reversed, but the pressure conditions being substantially identical. Likewise, it will be evident that the practice of this invention is not limited to gear pumps and motors employing any particular design of tooth but may be extended to any rotary device operating on the principle of displacing fluid by alternate spaces and projections on a pair of mating members.

Operation of the embodiment of Figure 3 Assume that the gears l5 and l! are being rotated in the same direction as they are in Figure 3. The chamber 2| is the discharge chamber and the pressure therein tends to produce a thrust on the gears 16 and I! which is balanced by the equal and opposite thrust on the said gears accomplished by the bores 23.

In addition to the balancing of the gears, the fluid entrapped in any of the tooth spaces on either of the gears by the tooth entering the said space is permitted to pass through the bore 23 into the space 24 or 25 and thence through the adjacent bore 23 to the discharge chamber 2|. This action will become apparent upon reference to the tooth and tooth space at l8 in Figure 3 wherein the tooth space is connected by the bore 23 with the opposite tooth space which is in communication with the notch 24. The notch or spac 24 is of sufficient length to be in communication with the next tooth space bore 23 associated there-.

and thence through the with with the discharge chamber 2|. it continues to rotate the tooth space opposite the one at 18 moves out of fluid communication with the notch 24 and hence no leakage from the discharge port to the inlet port takes place.

Thus, it will be seen that the construction of Figure 3 provides for a fully hydraulically balanced gear pump or motor while simultaneously providing for the release of the entrapped fluid at the point of mesh with the gears. Also, it will be seen that the fluid relieved from the tooth spaces is directed to the discharge port and thus enhances the capacity and efficiency of the device.

It will be apparent, as in the case of the em- As the gear bodiment of Figures 1 and 2, that the practice of this invention according to the embodiment of Figure 3 is not limited to any particular tooth contour but may be employed in connection with any fluid operable pump or motor which operates on the same principle as the one illustrated in Figure 3.

Accordingly, it will be understood that it is desired to comprehend such modifications of structure and arrangement as may be considered to come within the scope of the appended claims and the invention.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In combination in a gear pump, a casing having an inlet chamber and an outlet chamber, a pair of meshing gears rotatably mounted in said casing, each of said gears comprising an even number of teeth and intervening tooth spaces, a channel hydraulically connecting each of said tooth spaces with the tooth space directly opposite, and means comprising a passage in the wall of said casing for efiecting fluid communication between the channels connected with the tooth spaces of each gear which are engaged by a tooth on the other gear with the next adjacent of said channels which opens into said outlet chamber.

2. In a pump, a casing, a pair of intermeshing gears journaled in said casing, said gears defining with said casing, inlet and outlet chambers, each gear having the tips of its teeth in sliding engagement with the casing wall for more than of rotation, separate axially-spaced bores connecting the root space between each tooth of one gear with the diametrically opposite root space thereof, and channel means in the casing wall in continuous communication with one of said chambers and positioned to successively communicate with one end of each of said bores during the time the other end thereof is closed by an intermeshing tooth of the other gear.

3. In a pump, a casing, a pair of intermeshing gears joumaled in said casing to form with said casing, intake and outlet chambers, each gear having the tip of its teeth in contact with the casing walls throughout substantially 180 of its pitch circle, each gear having separate axially-' spaced passageways connecting oppositely disposed pairs of root sections between teeth, there being notches in the casing wall substantially greater incircumferential extent than the pitch of said gears and located to successively connect one end of each passageway with the next adjacent of said passageways as the other end of the first mentioned said passageway is closed by a tooth of the other gear.

- 4. In a pump, a casing having a pair of intermeshing gears journaled therewithin on parallel axes defining a plane, said gears. forming with said casing, intake and exhaust chambers having inlet and outlet connections, respectively, each gear having passageways connecting oppositepairs of root sections between teeth, respectively, each passageway being separate from the others, and channels in the wall of said casing on the inlet side of said plane, each of said passageways as it is instantaneously closed by the intermeshing tooth of the other gear, being connected through one of said channels with the passageway next adjacent. I

WALTER ERNST.

REFERENCES CITED The following references are of record in the file of thispatent:

UNITED STATES PATENTS 

